Heat Equation
Heat energy
(calories)
Example:
Mass (g)
Specific
heat
calorie
( gram ºC )
Change in
temperature ( ºC )
How much heat is needed to raise the temperature of
250 grams of water from 20ºC to 40ºC ?
1. Identify the variables
in the equation.
2. Plug the variables into the
equation and solve.
Heat equation: Q = mc
Q = trying to determine
m = mass of water = 250 grams
c = specific heat of water
= 1 calorie/g ºC
= 40ºC - 20ºC = 20ºC
calorie
Q = (250 g x 1 g
x (20ºC )
ºC
Q = 5000 calories
Differences in Specific Heat
HIGH SPECIFIC HEAT
Temperature goes up 1ºC
100 g
Water
100 calories
LOW SPECIFIC HEAT
Temperature goes up 20ºC
100 g
Iron
100 calories
When the same amount of heat is added to 100 grams of
water and 100 grams of iron, the iron's temperature gain
is 20 times the temperature gain of the water.
Specific heat is inversely related to temperature gain
Conduction
Conduction is the transfer of heat by the direct contact of particles
of matter. The molecules in the hot cup of liquid transfer their heat
energy to the molecules in the cold spoon.
Convection
Convection is the transfer of heat by the actual motion
of a fluid (liquid or gas) in the form of currents.
Danger!
Radiation
Radiation is heat transfer by electromagnetic waves.
Electromagnetic radiation from the sun heats Earth.
SUN
A Seabreeze Convection Cycle
High
Low
Air expands Air compresses
Low
High
Chlorofluorocarbons (CFCs)!
and Ozone Depletion
1
The ozone layer protects
Earth from ultraviolet light.
2
CFC's reach the stratosphere, destroying ozone.
3
O2 doesn't block ultraviolet light from the sun.
UVB rays
UVB rays
CFC
CFC
O2
UVB
CFC
UVB
O2
O2
Energy in the Atmosphere
What happens to the incoming solar radiation?
5% Scattered by
atmosphere
3% Absorbed by
ozone in the atmosphere
(almost all of the
ultraviolet light)
Sun
22% Reflected
by clouds
17% Absorbed by
atmospheric gases
water vapor & dust
3% Reflected by the
Earth's surface
50% Absorbed by Earth's surface
Why Does Earth Have Seasons?
June
N
January
or
S o th e
u t rn H
he
em
rn
i
He s p h e r
e
mis
phe
re
N
or
S o th e
u t rn H
he
em
rn
i
He s p h e r
e
mis
phe
re
Earth's orbit around the sun is almost a perfect circle. Earth
has seasons because it spins on its axis at an angle. When the
northern hemisphere is tilted toward the sun in June, the sun's
rays are more intense. When the northern hemisphere is tilted
away from the sun in January, the sun's rays are more diffuse.
Global Surface Wind Patterns
H
H = High pressure
L = Low pressure
L
H
Pola
r
g We
Trad
e
Trad
e
Prev
ailin
L
erlie
Prev
ailin
L
H
East
H
sterl
ies
30º
Wind
s
s
0º
sterl
East
60º
Wind
g We
Pola
r
s
erlie
ies
s
30º
60º
~ Southern Oscillation
The El Nino
Pacific Ocean
Pacific Ocean
Indonesia
Current
flows west
Peru
The usual pattern of current flow
Coast of Peru
Normal current direction
Up-welling
cold currents
containing
nutrients
Usually, cold water from ocean depths
flows up to the surface along the
coast of Peru.
Indonesia
Current
reverses
direction and
flows east
Peru
The current reverses direction
~
during El Nino.
Warm water
Coast of Peru
Nutrients blocked
by the warm water
~ the warm water current
During El Nino,
acts like a lid over the cold water.
The Rainshadow Effect
20º C
Prevailing
wind
direction
Fertile land
40º C
Desert
40º C